Amyloid deposits and loss of neurones in the claustrum of the aged dog.

In dogs under 17 years of age no amyloid deposits were observed in the claustrum. After that age amyloid deposits were found in all the brains studied. The number of amyloid deposits increases rapidly between 17 and 19 years of age. In none of the animals were neurofibrillary tangles found. However, in almost all claustra with amyloid deposits the number of neurones was smaller than in those without amyloid pathology. The loss of neurones resulted in a decrease in the volume of claustrum, which is about 22% smaller in dogs over 17 years of age than in younger animals. No considerable age-related differences were found in the average size of neurones and their nuclei.